关于数据库查询语句的报错

-- 利用窗口函数
select *
from (select *,
row_number() over (partition by 课程号 order by 成绩 desc) as ranking
from chengji) as a
where ranking ‹= 2;
表格在这
https://ask.csdn.net/questions/7766276?spm=1001.2014.3001.5501

select *
from (
         select *,
                row_number() over (partition by 课程号 order by 成绩 desc) as ranking
         from chengji
     ) as a
where a.ranking <= 1;

获取各科最高分